Catalytic oxidative dehydrogenation of ketones with improved supported gold catalyst

ABSTRACT

An improvement is provided in a process in which ketones and mixtures of ketones and alcohols having at lest one pair of hydrogen atoms on the alpha and beta carbon atoms are oxidatively dehydrogenated to the corresponding ethylenically unsaturated ketone by contacting the ketone and molecular oxygen-containing gas with a catalyst containing a metal of Group IB (Cu, Ag, Au) in the vapor phase (400*-750*C.). The catalyst can be a Group IB metal or oxysalt and can be on a support. Gold and supported gold catalysts are particularly preferred. The improvement is in obtaining high selectivity by the use of a supported gold catalyst (1-50 percent gold) in which the support is a clear, transparent, single crystal alpha-alumina having at least 50 percent and preferably 75 percent of its surface area covered with gold.

nite States atent Etherington, Jr. et a1.

[ 54] CATALYTEC ()XHDATIVE DEHYDROGENATION OF KETONES WITH INWROVEDSUPPORTED GOLD CATALYST [72] Inventors: Robert W. Etherington, Jr.,Pennington; Koei-Liang Llauw, Murray Hill, both of [73] Assignee: MobilOil Corporation [22] Filed: Nov. 3, 1969 [211 Appl. No.: 873,705

Related U.S. Appllcatlon Data [63] Continuation-in-part of Ser. No.711,864, March 11,

1968, Pat. No. 3,476,808, which is a continuation-inpart of Ser. No,639,029, May 17, 1967, abandoned.

[56] References Cited UNITED STATES PATENTS 2,101,820 12/1937 Woodhouse..260/601 3,156,735 11/1964 Armstrong .260/596 [451 June 27, 1972Primary ExaminerBemard Helfin Assistant Examiner-Norman MorgenstemAttorney-Oswald G. Hayes, Andrew L. Gaboriault and Hastings S. Trigg[57] ABSTRACT An improvement is provided in a process in which ketonesand mixtures of ketones and alcohols having at lest one pair of hydrogenatoms on the alpha and beta carbon atoms are oxidatively dehydrogenatedto the corresponding ethylenically unsaturated ketone by contacting theketone and molecular oxygen-containing gas with a catalyst containing ametal of Group [B (Cu, Ag, Au) in the vapor phase (400-750C. Thecatalyst can be a Group 1B metal or oxysalt and can be on a support.Gold and supported gold catalysts are particularly preferred. Theimprovement is in obtaining high selectivity by the use of a supportedgold catalyst (1-50 percent gold) in which the support is a clear,transparent, single crystal alphaalumina having at least 50 percent andpreferably 75 percent of its surface area covered with gold.

3 Claims, No Drawings CATALYTIC OXIDATIVE DEI'IYDROGENATION OF KETONESWITH IMPROVED SUPPORTED GOLD CATALYST CROSS-REFERENCES TO RELATEDAPPLICATIONS This application is a continuation-in-part of co-pendingapplication serial number 711,864, filed Mar. 11, 1968, now U.S. Pat.No. 3,476,808, which in turn is a continuation-inpart of applicationserial number 639,029, filed May 17, 1967, and now abandoned.

BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This inventionrelates to oxidative dehydrogenation. It is more particularly concernedwith selective catalytic oxidative dehydrogenation of ketones tounsaturated ketones.

2. DESCRIPTION OF THE PRIOR ART Various methods have been proposed toprepare unsaturated ketones, such as 2-cyclohexen-l-one. Many give lowyield of product. Others involve reactants that are either relativelyexpensive or not readily available or both. For example, it has beenproposed to oxidize cyclohexen to 2-cyclohexen-1- one (U.S. Pat. Nos.,2,992,272 and 2,369,182). Another procedure involves dehydrobrominationof 2-bromocyclohexanone [1. Chem. Soc., 607 (1954)]. The procedure setforth in Organic Syntheses uses 3-ethoxy-2-cyclohexanone as the startingmaterial [Org Syn., 40, 14 (1960)]. A recent patent (U.S. Pat. No.3,050,561) described a route using vinyl-cyclohexene. A Birch reductionof anisole gives 2- cyclohexen-l-one in about 20 percent yield in smallscale reactions [1. Chem. Soc., 430 (1934)]. Larger scale reactions,however, are very hazardous. Insofar as is now known, it has not beenproposed to prepare 2-cyclohexen-l-one or other unsaturated ketones byselective dehydrogenation of the corresponding saturated ketone.

SUMMARY OF THE INVENTION This invention provides a process for producingan unsaturated ketone that comprises contacting a ketone reactant and amolecular oxygen-containing gas, in the vapor phase, with a catalystconsisting of metallic gold or metallic gold on a support, theimprovement that comprises using a supported metallic gold catalyst inwhich the support is a clear, transparent, single crystal alpha aluminahaving at least 50 and preferably 75 percent of its surface covered withgold.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS The ketone reactant used in theoxidative dehydrogenation process is a ketone having at least 1 pair ofalpha and beta carbon atoms with at least 1 hydrogen atom on each. Itcan be an open chain ketone or a cyclic ketone. Typical ketone reactantsare: ethylphenyl ketone; butanone (methylethyl ketone); pentanone-2;pentanone-3; hexanone-2; Z-methyI-pentanone- 3; heptanone-4;2,4-dimethylpentanone-3; heptanone-3; 2- methyl-hexanone-5; octanone-3;4-methylheptanone-5; octanone-2; nonanone-2; nonanone-S; decanone-Z;decanone-4; undecanone-2; undecanone-3; tetradecanone-3; cyclopentanone;cyclohexanone; 3-methylcyclohexanone; cycloheptanone; and2,S-dimethylcyclohexanone. The term ketone reactant" includes mixturesof ketone and the corresponding alcohol, such as a mixture ofcyclohexanone and cyclohexanol.

In the oxidative dehydrogenation process, the molar ratio of molecularoxygen to ketone reactant can be between 0.1 and 3, but preferably it isbetween 0.2 and 2. Pure oxygen can be used, but generally mixturescontaining molecular oxygen are used, such as air, mixtures of air andoxygen, and mixtures of oxygen with nitrogen.

The catalyst utilizable in the oxidative dehydrogenation processcomprises a metal of Group 18 of the Periodic Chart of the Elements. ThePeriodic Chart referred to is that appearing on pages 58-59 of LangesHandbood of Chemistry,

seventh edition (1949). The preferred catalysts are metallic. They canbe in the form of wire, gauze, pellets or coating on a support. It isalso within the contemplation of this invention to use these metals inthe form of oxides and oxysalts, usually but not necessarily on support.The catalyst supports can be any inert refractory material such asalumina, silicon carbide, and Alundum When supported, the amount ofcatalytic metal, oxide, or oxysalt in the catalyst can vary widelybetween about 1 and about 50 percent or more, by weight. Especiallypreferred catalysts are metallic gold and supported metallic gold.

The catalyst used in the improved process of this invention is asupported gold catalyst. The support used is a clear, transparent alphaalumina, as shown by examination under an optical microscope. In orderto provide good selectivity, it is es sential that at least 50 andpreferably 75 percent of the surface of the support is covered withmetallic gold. If large areas of the support are left uncovered, sidereactions occur, including degradation and cracking of cyclohexanone orother ketone reactant. It has been found that catalysts having poorselectivity are obtained when the alpha-alumina support has an unclearcloudy reactant. on examination under an optical microscope. The supportsurface can be coated with gold by any means known in the art ofpreparing supported metallic catalysts. For example, clear alpha aluminabeads are covered with an aqueous solution of gold trichloride ofsufficient concentration to give the desired amount of gold in thefinished catalyst. Then, the mixture is evaporated to dryness and thegold salt is reduced to metallic gold. The support can also be coatedwith a hydrocarbon solution of an organic gold compound, such as goldterpene mercaptide, followed by heating at an elevated temperature in anoxidizing atmosphere.

The oxidative dehydrogenation reaction is carried out in the vapor phaseat temperatures varying between about 400C. and about 750C, preferablybetween about 500C. and about 700C. The contact time of cyclohexanonewith the catalyst can be between about 0.001 sec. and about 20 see. Inthe preferred continuous operation, cyclohexanone is charged at a LHSV(Volume liquid charge per volume catalysts per hour) of 0.1 to 20.

Any vessel suitable for carrying out exothermic vapor phase reactions isutilizable herein. The process can be carried out batch wise, but it ismore suitably carried out in a continuous process. In such an operation,unreacted ketone reactant can be recycled to extinction, afterseparation from the product and the small amount of by-product, phenolin the case of cyclohexanone. It should be noted that the phenolby-product has many well known uses, e.g., in manufacture of phenolicresins.

EXAMPLE 1 A copper catalyst was prepared by mixing a solution of 50.7 g.of cupric chloride in g. of distilled water with 270 g. of Va X Vssilicon carbide pellets and evaporating the mixture of dryness.

A 75 ml. portion of the dry catalyst was placed in a 24 mm. l.d. X 14inches long vertically mounted high-silica glass (Vycor) tube reactorcontaining a concentric 7 mm. Vycor thermocouple well. The portion ofthe reactor above the catalyst bed was packed with inert pellets to actas a mixing and preheating section. The reactor was enclosed in anelectric tube furnace.

The catalyst bed was slowly heated to 500C. in a stream of air and wasmaintained at this temperature overnight. A mixture of air andcyclohexanone vapor was passed over the catalyst for several hours tocondition the catalyst. A mixture of air and cyclohexanone vapor wasthen introduced to the reactor at the rates of 0.0062 moles of 0 /min.and 0.0046 moles of cyclohexanone/min. The maximum bed temperature wasin the range of 6l8-630C. The condensed organic products, afterseparation of a small aqueous layer, contained 84 percent unreactedcyclohexanone, 13.3 percent 2- cyclohexen-l-one, and approximately 3percent phenol.

EXAMPLE 2 A 75 ml. bed of silver catalyst (4 percent) silver on ,6 X A:inches alundum pellets) was placed in a vertically mounted inch i.d.stainless steel pipe reactor containing a concentric 5 inch stainlesssteel thermocouple well. A mixing and preheating bed of inert aluminapellets was placed on top of the catalyst bed. The reactor was heatedwith an electric tube furnace.

Cyclohexanone was pumped at the rate of 0.62 ml./min. Through a heatedtransfer line acting as a vaporizer to the top of the reactor where itwas mixed with air (525 std. cc./min.) and nitrogen (1,571) std.cc./min. The maximum bed temperature was 575C. The gaseous reactionmixture leaving the reactor was passed through the series of condensers.The condensed organic product was analyzed by gas chromatography and wasfound to contain 76 percent cyclohexanone, 18 percent2-cyclohexen-l-one, and 6 percent phenol.

EXAMPLE 3 In a reactor similar to that of Example 2, the catalyst bedconsisted of a 60 ml. section packed with discs of 20 mesh silver gauze.Cyclohexanone was pumped at the rate of 1.57 ml./min. through thevaporizer, was mixed with 1,700 std. cc./min of air and 2,500 std.cc./min. of nitrogen. The maximum catalyst bed temperature was 650C. Thecondensate obtained from the reaction mixture after 88.8 g. ofcyclohexanone has been fed consisted of 10.4 g. of an aqueous layer and75.6 g. of an organic layer. The organic layer was analyzed by gaschromatography. It was found to contain 4.8 g. of dissolved water, 49.7g. of cyclohexanone, 18.5 g. of 2- cyclohexen-l-one, and 2.6 g.ofphenol.

EXAMPLE 4 A gold catalyst was prepared by evaporation of a goldtrichloride solution (aqueous) in the presence of A; X Vs inch pelletsof inert alumina 1 M lg. surface area. The catalyst containedapproximately 4 percent gold, calculated as the metal. A 54 ml. portionof the dried catalyst was placed in a inch d. 14% inch copper tubereactor in an electric furnace. The catalyst was heated at 400C.overnight in a stream of air. A mixture of cyclohexanone vapor (0.0033g. mole/min.) and air (0.0107 g. mole 0 lmin.) was passed through thecatalyst bed. The maximum bed temperature was measured on the outsidewall of the reactor was 560C. The condensed organic product contained64.1 percent unreacted cyclohexanone, 30.8 percent 2-cyclo-hexen-l-one,and 5.1 percent other products, mostly phenol.

EXAMPLE 5 In a reactor similar to that of Example 2, the catalyst bedconsisted of a 32 ml. section packed with inch lengths of 30 gauge wire.Cyclohexanone was pumped at the rate of 1.45 ml./min. through thevaporizer, was mixed with 1,800 std. cc./min. of air and 2,500 std.cc./min. of nitrogen. The maximum catalyst bed temperature was 600C. Thecondensate obtained from the reaction after 130.4 g. of cyclohexanonehad been fed consisted of 102 g. of cyclohexanone, 25.7 g. of2-cyclohexen-l-one, 1.5 g. of phenol and 1.5 g. of water, by gaschromatographic analysis.

EXAMPLE 6 In a titanium pipe reactor similar in design to the stainlesssteel pipe reactor of Example 2, the catalyst bed was a 32 m1. sectionpacked with a catalyst consisting of 10 percent gold on a 3/16 inchspherical ceramic Support. Cyclohexanone was pumped at the rate of 2.34ml./min. through the vaporizer, was mixed with 450 std. ml./min. of airand 2,500 std. ml./min. of nitrogen. The maximum catalyst bedtemperature was 600C. The condensate obtained from the reaction of 203.2g. of cyclohexanone consisted of 159 g. cyclohexanone, 33.2 g. of2-cyclohexen-1-one, and 1.8 g. of phenol, and 3.9 g. of water.

The 2-cyclohexen-l-one produced in accordance with this invention is aprecursor for manufacture of 4-benzothienyl N- methylcarbarnate, ahighly effective pesticide. The 2- cyclohexen-l-one can be converted toS-mercaptocyclohexanone, e.g., by reacting a benzene solution of thecyclohexenone with hydrogen sulfide at room temperature.3-Mercaptocyclohexanone is then reacted with 2,2-dichloroacetaldehyde at-l00C. in the presence of a protic acid catalyst (l-lCl) to form4-oxo-4,5,6,7-tetrahydrobenzothiophene (see U.S. Pat. No. 3,346,591).The 4-oxo-4,5,6,7- tetrahydrobenzothiophene can then be dehydrogenatedto 4- hydroxybenzothiophene by several methods such as that of Fieser etal., .1. Am. Chem. Soc., 57, 1611 (1935). The 4- hydroxybenzothiophenecan then be converted to 4- benzothienyl N-methylcarbamate by methodsfully detailed in U.S. Pat. Nos, 3,288,673 and 3,288,808. These patentsalso demonstrate the pesticidal effectiveness of this material.

As indicated hereinbefore, the process of this invention is applicableto other acyclic and cyclic ketones. The following examples illustratethe use of some other ketones with the preferred metallic gold.

EXAMPLE 7 A reactor described in Example 2 was filled with 70 cc. of x;X 54; inch alundum followed by 60 cc. of catalyst consisting of 10percent gold deposited on 3/ 16 inch spheres on inert alumina. Thereactor was heated with an electric tube furnace.

Cyclopentanone was pumped at the rate of 1.1 ml./min. through a heatedtransfer line functioning as a vaporizor to the top of the reactor whereit was mixed with both air being pumped at the rate of 800 std. cc./min.and nitrogen at 800 std. cc./min. The mixture of the gases then passedthrough the heated catalyst bed. The maximum temperature of the catalystbed was 566C. The product contained 20.2 percent 2- cyclopenten-l-one,and 79.3 percent unreacted cyclopentanone.

EXAMPLE 8 With the same reactor as in Example 7, 3-methylcyclohexanone,fed at 1 ml./min., air fed at 700 std. cc./min., and nitrogen fed at 700std. cc./min. were preheated, mixed, and then passed through thereactor. The maximum temperature of the catalyst bed was 572C. Theorganic product contained 12.4 percent 5-methyl-2-cyclohexen-1-one,- 9.2percent 3- methyl-2-cyclohexen-l-one, and 78.4 percent unreacted 3-methylcyclohexanone.

EXAMPLE 9 With the same reactor as in Example 7, heptan-4-one, fed at lml./min., air fed at 800 std. cc./min., and nitrogen fed at 800 std.cc./min were preheated, mixed, then passed through the reactor. Themaximum temperature of the catalyst bed was 552C. The product contained9.9 percent 2-haptene-4-one, 1.9 percent 2,5-heptadien-4-one, and 86percent unreacted heptan-4-one.

EXAMPLE 10 EXAMPLE 1 l A reactor similar to that of Example 2, except 18inches in length, was filled with 32 cc. of 30 gauge gold wire cut intoA inch in length. A

Methyl ethyl ketone, fed at 1.8 ml./min., air fed at 1,800 std.cc./min., and nitrogen fed at 2,500 std. cc./min. were preheated, mixed,and then passed through the reactor. The maximum temperature of thecatalyst bed was 600C. The product contained 7.8 percent methyl vinylketone, 1.3 percent 2,3- butanedione, and 90.8 percent unreacted methylethyl ketone.

The following examples demonstrate a method of catalyst preparation andruns with a good catalyst and with an unsatisfactory catalyst with theresults of examination of these catalysts.

EXAMPLE 12 To a solution of 18 g. of chlorauric acid (HAuCl .H O) in 100ml. of water were added 200 g. of inch spheres of clear alpha alumina.The mixture was heated with stirring until it had been evaporated todryness. The dried spheres were placed in a reactor and heated at300-400C. in a stream of air for about 16 hours (overnight).

EXAMPLE 13 A 150 ml., 5 inch deep bed of a gold on alumina catalyst(designated Catalyst A) was placed in a 1 A inch I.D.

EXAMPLE 14 In the reactor described in Example 13 was placed a 150 ml.,5 inch deep bed of a different 10 percent gold on alumina catalyst(designated Catalyst B). Air fed at cu.ft./hr., nitrogen fed at 30cu.ft./hr., and cyclohexanone fed at 25 ml./min. were preheated,premixed, and passed through the catalyst bed for 12 hours. The maximumcatalyst bed temperature was l,050F. (566C). Liquid product recovery was87 percent. Of the liquid recovered 5.5 percent was 2-cyclohexen-l-one,92 percent was unreacted cyclohexanone, and less than 0.5 percent wasphenol. The conversion was 21.7 percent and the selectivity to2-cyclohexen-l-one was 17.7 percent.

It is to be noted that Catalyst A was much more selective than CatalystB. The unrecoverable non-condensables of 13 percent (Example 14) weredegradation products including 60, CO and C C. hydrocarbons. In order todetermine why two apparently similar catalysts behaved in such adifferent manner, they were examined by microscope and by X-raydiffraction.

EXAMPLE 15 A sample of each of Catalysts A and B was examined under anoptical microscope. 1n the case of Catalyst A, the support was clear,transparent single crystal alpha-alumina and about 75 percent of thesurface was covered with gold. In the case of the Catalyst B, thesupport was a milky alpha-alumina and only about 25 percent of thesurface was covered with gold. As indicated by X-ray diffraction, thegold average crystallite size was about 250 A. in Catalyst A and about450 A. in Catalyst B.

As was indicated hereinbefore, the process of this invention isapplicable to mixtures of cyclohexanone and cyclohexanol, illustrated inthe following example.

EXAMPLE 16 Through a 2% inch diameter, 7 inch long stainless steelreactor containing 10 ml. of inch long pieces of 30 gauge gold wire(equivalent in performance to Catalyst A, Example 13) was passed 65.8 g.of an equimolar mixture of cyclohexanol and cyclohexanone over atwo-hour period. The air flow was 260 ml./min., and nitrogen flow was260ml./min. Maximum catalyst bed temperature was 550C. The liquidproduct contained 1 percent cyclohexene, 62.2 percent cyclohexanone,28.2 percent cyclohexanol, 7.1 percent Z-cyclohexen-l-one, and 1.3percent phenol.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be resorted to, without departing from the spirit and scope of theinvention, as those skilled in the art will readily understand. Suchvariations and modifications are considered to be within the purview andscope of the appended claims.

What is claimed is:

1. In a process for producing an unsaturated ketone that comprisescontacting a ketone reactant selected from the group consisting of ethylphenyl ketone, butanone, pentanone-2, pentanone-3, hexanone-Z,2-methylpentanone3, heptanone-4, 2,4-dimethylpentanone3, heptanone-3, 2-methylhexanone-S, octanone-3, 4-methylheptanone-5, octanone-2,nonanone-Z, nonanone-S, decanone-2, decanone-4, undecanone-2,undecanone-3, tetradecanone-3, cyclopentanone, cyclohexanone, a mixtureof cyclohexanone and cyclohexanol, 3-methylcyclohexanone,cycloheptanone, and 2,5-dimethylcyclohexanone and a molecularoxygen-containing gas, in the vapor phase, with a catalyst consistingessentially of metallic gold on a support, at a temperature of betweenabout 400C. and about 750C. and for a contact time of between about0.001 sec. and about 20 sec., the improvement that comprises using asupported metallic gold catalyst in which the support is a clear singlecrystal alpha alumina having at least 50 percent of its surface coveredwith gold.

2. The method defined in claim 1, wherein said ketone reactant iscyclohexanone or a mixture of cyclohexanone and cyclohexanol.

3. The method defined in claim 1, wherein the catalyst is a clear singlecrystal alpha alumina having 75 percent of its surface covered withgold.

533 39 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,673,255 Dated June 27, 1972 Inventor(s) Robert w. Etherington Jr. andLoei-Lismg Lieuw It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 1 Line #6 "least 50" should be --least 50 percent-- Col. 2 Line 7Should be a period after Alundum Col. 2 Line 8 "about 1" should be-about 1 percent- Col. 2 Line 16 "least 50" should be -least 50percent-- Col. 2 Line 22' "cloudy reactant" should be --cloudyappearance-- 001. 2 Line 55 1/8 X 1/8" should be "1/8" X 1/8"-- Col. 2Line 55 "of dryness" should be -to dryness-- Signed and sealed this 6thday of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. The method defined in claim 1, wherein said ketone reactant iscyclohexanone or a mixture of cyclohexanone and cyclohexanol.
 3. Themethod defined in claim 1, wherein the catalyst is a clear singlecrystal alpha alumina having 75 percent of its surface covered withgold.